1. Field of the Invention
The invention relates generally to tourniquets. More particularly, aspects of the invention include tourniquets with self-locking features, and/or tourniquet timers that provide visual and tactile indicators based on pressure applied to the tourniquet.
2. Related Art
As known in the art, and as variously described in various of the below-identified references, a tourniquet is a device that is designed to be applied to a limb for the purpose of constricting blood flow to that limb by applying pressure in order to limit the effects of extreme blood loss.
Tourniquets are typically used in the temporary treatment of extremity injuries, i.e. damage to the body's arms and legs. The severity of an extremity injury depends on the location and path of the injury. Critical conditions are commonly associated with compromised vascular components of the particular extremity. Vascular injuries to the extremities become critical when life threatening blood loss is possible.
When a major artery is severed, either by injury or surgical intervention, controlling blood loss becomes vital. In severe cases, where potential blood loss is considered life-threatening, a tourniquet may be applied proximal to the vascular disruption to manage blood loss. Because of its rapid blood flow occlusion capabilities, the tourniquet is commonly considered a life-saving device in emergency situations.
Even though civilian extremity injuries are common, extremity injuries occurring in the battlefield are more frequent and can present unique challenges. Therefore, many emergency tourniquets are specialized for use on the battlefield. In general, the goal of such tourniquets is to extend the survival time of a casualty until the patient can reach additional medical aid.
Knowledge of tourniquet application time serves as a determining factor for the method of treatment once an individual reaches a medical facility. Specifically it allows clinicians to estimate the amount of blood loss and the extent of the extremity injury. Based upon tourniquet application time and other signs, e.g. hematoma, hemorrhage, or acute ischemia, the patient will be diagnosed and the severity of injury will be scored using the injured extremity index. Monitoring application time is also important with regard to the side effects of tourniquet application and may also play a part in determining the extent of an extremity injury.
Tourniquet application time is also important to account for readjustment periods. A tourniquet must remain extremely taught to prevent severe blood loss. However, extreme pain is commonly associated with blood occlusion caused by a tourniquet. The pain, caused by hypoxia becomes so extensive in certain cases that some victims loosen the tourniquet to allow some blood flow distal to the tourniquet application site which therefore alleviates some of the pain. The individual later retightens the tourniquet. This process may occur multiple times over the period of transportation to a medical facility. However, when the individual reaches medical help this information is rarely transferred to the medics even though the non-uniform occlusion may alter the treatment plan.
The pressure applied by an emergency tourniquet may in some configurations be controlled by the user. Pain associated with tourniquet application or accompanying injuries, may prevent or inhibit an individual from tightening the tourniquet to the proper level. Also, the user may not know the appropriate tension to occlude severe blood loss.
U.S. Pat. No. 4,321,929 to Lemelson, et al. describes an automatic tourniquet with a control system. An electronic sensing means senses physiological variables and generates signals which are applied to the computer or microprocessor, which analyzes such signals and generates control signals for controlling the motors operating pumps. A timer is provided for controlling the automatic tourniquet and providing intervals of time during which blood pressure is sensed and the tourniquet is tightened.
U.S. Pat. No. 6,746,470 describes a pneumatic tourniquet adapted for self application. In particular, the tourniquet comprises a bladder cuff with a clamp means for securing the bladder around the limb and an indicator module connected to the bladder. The indicator module indicates cuff pressure and elapsed inflation time interval and is supplied with a microprocessor and an alarm indicator that provides an audible and visual indication of alarm. The microprocessor is programmed to determine elapsed inflation time by measuring the duration of time that the pressure has exceeded a predetermined pressure threshold. The alarm indicator may also be activated by microprocessor if unusually high pressures are detected in the bladder (for example pressures greater than 400 mmHg).
U.S. Patent Application Publication No. 2010/0234877 by Pienkowski et al. describes an “electromechanical” tourniquet with a force sensor to measure occlusive pressure applied along a line extending into the limb of a person as well as a user interface that displays duration of use. The tourniquet includes a microcontroller connected to the force sensor as well as a battery and a voltage regulator. A power button of the tourniquet may be activated and an extremity selector switch set to define the extremity and/or location of tourniquet application.
U.S. Patent Application Publication No. 2008/0177159 by Gavriely describes a timer for tourniquets that generates two or more warnings, for example, both an advance warning that a usage time is about to expire and a final warning when a usage time expires and a danger time begins. The generating of the first and/or the second warning may be accompanied by sound and/or light signals, and/or a wireless transmitted warning.
U.S. Patent Application Publication No. 2010/0160957 by Kirkham describes a one-handed loop tourniquet that includes an elongate cord and a cleat with at least two recesses for receiving and securing an end of the elongate cord during use as a tourniquet. In use, the free end of the cord is passed through a loop of the cord so that the cord extends around the limb to which the tourniquet is being applied, and then the free end of the cord is locked into the cleat using the recesses.
Despite many advances in the design and use of tourniquets, there still exist limitations in the effectiveness of various implementations, particularly in the context of rapid and reliable application and monitoring of the tourniquet in conditions that may typically be found on the battlefield and other emergency situations. For example, the use of various known electronic monitoring and control means may be susceptible to shock, pressure, moisture, dirt, etc. routinely found in battlefield conditions. Other tourniquet configurations that may be adapted for one person to use may also suffer from drawbacks in their performance, and/or clinical effectiveness, due to accommodations made to suit one-handed use. For example, the cord tourniquet such as described in Kirkham, and other known means, may lack the desired ability to properly set and/or distribute the necessary pressure applied by the tourniquet to effectively stop extremity bleeding including arterial bleeding.
Accordingly, there exist ongoing needs for improved tourniquet devices that are adapted for on-hand use and/or include robust, and easy to use, reuse and/or monitor, timing devices.